1. Field of the Invention
The present invention relates generally to catheters having an expandable balloon and to premounted balloon expandable stent balloon catheters, and specifically to a dilatation balloon catheter with a balloon protector means or a stent delivery system with a balloon and stent protector means.
2. Description of Related Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure which is well established for the treatment of blockages in the coronary arteries. Blockages may occur from cholesterol precipitation on the coronary wall which may be in any stage from initial deposit through aged lesions. Coronary arteries may also become blocked due to formation of thrombus.
The most widely used form of percutaneous coronary angioplasty makes use of a dilatation balloon catheter. In typical PTCA procedures, the cardiovascular system of a patient is accessed with an introducer, usually in the groin area. All other devices including a guiding catheter are percutaneously introduced into the cardiovascular system of a patient through the introducer and advanced through a vessel until the distal end thereof is at a desired location in the vasculature. A guide wire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guide wire sliding through the dilatation catheter. The guide wire is first advanced out of the guiding catheter into the patient's coronary vasculature and the dilatation catheter is advanced over the previously advanced guide wire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a fluid at relatively high pressures, such as greater than about four atmospheres, to radially compress the atherosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.
In angioplasty procedures of the kind described above, there may be restenosis of the artery, which either necessitates another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To reduce restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, called a stent, inside the artery at the lesion. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel of the body of a living human or in some other difficulty accessible place. A stent generally has a diameter which may be increased or decreased. Stents are particularly useful for permanently widening a vessel which is in a narrowed state, or for internally supporting a vessel damaged by an aneurysm.
Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon, to place it in a selected location in the body cavity. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Stents delivered to a restricted coronary artery, expanded to a larger diameter by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer and U.S. Pat. No. 5,007,926 to Derbyshire.
One important characteristic of a dilatation balloon catheter is its "profile", which is determined by the outer diameter (O.D.) of the distal end portion of the balloon and stent when deflated. The outer diameter affects the ease and ability of the dilatation catheter to pass through a guide catheter, through the coronary arteries, and across a tight lesion. Considerable effort has been made in developing low profile dilatation balloon catheters. U.S. Pat. No. 5,342,307, incorporated herein by reference, discloses a balloon protector sleeve used with a tri-fold dilatation balloon catheter for angioplasty.
Minimization of "profile" is of importance in balloon catheters and stent delivery systems. Accordingly, the present invention is particularly directed to improved arrangements of balloon catheters having a balloon protector and stent delivery systems having a balloon and including a stent protector means which provide a minimized profile.